Typical removable data storage devices rely on rotation of the data storage media about a hub to record and read data. Examples of such removable devices include magnetic data storage discs, magnetic data storage tape cartridges, and magneto-optical discs.
Removable magnetic data storage discs typically include a polyester resin or the like having a magnetic layer on each side thereof on which information is recorded by a magnetic head. Flexible magnetic data storage discs which have a diameter of 31/2 inches (90 mm) or less are known as micro-floppy discs and will be referred to so herein. Generally, the micro-floppy disc is accommodated in a hard casing to form a cartridge.
The flexible magnetic data storage disc comprises a thin circular magnetic recording medium having a hub at its center. The hub serves as a means of rotating the recording media over recording heads. Typical hubs are made of AISI/SAE 430/431 Stainless Steel because of its durability, corrosion resistance, and susceptibility to magnetic attraction. Some hubs are provided in uncoated stainless steel, while others have been coated with chrome or epoxy to enhance their appearance or wear properties.
The disc hub plays an important role in proper operation of the disc. FIG. 1 is an exploded view of a typical micro-floppy disc drive spindle 10 and hub 20, including an annular ring of magnetic media 21 attached to the hub 20. The drive spindle 10 includes a center pin 12 and alignment pin 14 that is spring-loaded to be biased away from the center pin 12. The center pin 12 is received in the center pin opening 22 of the hub 20 while the alignment pin is received in the alignment window 24.
FIG. 2 is a top view of the hub 20 properly mounted on a drive spindle 10 in which the center pin 12 of the drive 10 is received in the center pin opening 22 and the alignment pin 14 is properly located in the alignment window 24. As shown, the alignment pin 14 is urged towards the center pin 12 during rotation of the hub 20 (and attached recording media--not shown) by the window 24. The drive spindle 10 is typically magnetized to attract the hub 20 towards the drive 10 during loading and use of the disc. Although proper seating and orientation of the hub on the drive typically occurs without fault, there are a number of errors which can occur that cause errors in the writing or reading of data from the media.
FIG. 3 depicts one error that can occur in seating of the hub 20 on drive spindle 10. This error involves failure of the alignment pin 14 to properly seat in the alignment window 24 in hub 20. As shown, the alignment pin 14 has only moved partially towards its proper position in the comer of the window 24. This error prevents proper positioning of the recording media relative to the read/write heads in the disc drive. Errors of the this type are typically detected with a test commonly referred to as "Index to Data."
FIGS. 4 and 5 depict another error in seating of the hub 20 on the drive spindle 10. This error, referred to as a "mischuck," results in lifting of the hub 20 off of the drive spindle 10 in the area of the alignment pin 14. As a result, the hub 20 is canted on the drive spindle 10 and proper alignment of the media with respect to the read/write heads in the disc drive cannot be maintained. That improper alignment typically results in modulation errors as data is read from and written to the disc.
Similar concerns can plague manufacturers and users of other rotating removable data storage devices that incorporate a hub that mates with a spindle to rotate the data storage media, whether that media stores data magnetically or optically. Examples of such devices include removable magnetic data storage discs other than micro-floppy discs, removable magnetic data storage tape cartridges, and magneto-optical data storage discs.
Although the errors discussed above occur infrequently and are typically tested for by manufacturers of high quality removable data storage devices, any improvements that further reduce their incidence can be extremely valuable in terms of improved manufacturing yields in addition to increasing the reliability of the devices in use by purchasers.